1. Field of the Invention
The invention relates to an apparatus for forming barbs on a filament and the component parts of the apparatus.
2. Description of the Prior Art
In the prior art, it is well known that surgical and traumatic wounds are typically closed with a filament introduced into the tissue by a needle attached to one end. Closure of the wound and holding tissues together supports healing and re-growth. What is typically used for this procedure is known as a suture.
A barbed suture is a one-way suture which allows passage of a needle-drawn suture in one direction through tissue, but not in the opposite direction. A barbed suture is generally an elongated body having a pointed leading end and a plurality of axially and circumferentially spaced barbs on the exterior surface of the elongated body.
In closing a wound with a barbed suture, the suture is passed through tissue at each of the opposed sides of a wound. Suture pairs are formed in which trailing ends of sutures are positioned generally in alignment at opposite sides of the wound. On insertion of each suture, the needle is pushed to extend out of the tissue at a point laterally remote from the wound, then the needle is pulled out to draw the suture to the desired position. The suture may then be severed from the needle or inserted again. (Note that methods of using barbed sutures are disclosed in copending U.S. patent application Ser. No. 09/943,733, “Method of Forming Barbs on a Suture and Apparatus for Performing Same,” the disclosures of which is incorporated herein by reference.) These methods are also described in International Patent Application, PCT/US02/27525. One advantage of using barbed sutures is that there is an ability to put tension in the tissue with the result of less slippage of the suture in the wound. Another advantage is that barbed sutures do not require tying as in prior art suturing methods. The number of suture pairs is selected in accordance with the size of the wound and the strength required to hold the wound closed. Although tissue anchoring is easier with a very pointed barb and a relatively skinny tip, better tissue holding results are obtained with a fuller tip barb.
In some circumstances of tissue repair, a random configuration of barbs on the exterior of the suture is preferred. With as many barb angles as possible, superior wound holding may be achieved. However, in other circumstances where the wound or tissue repair needed is small, a small suture is preferable. A thin suture may require a reduced number of barbs on the exterior of the suture.
In other circumstances the use of two-way barbed suture is preferable. A two-way barbed suture is one that has barbs permitting passing of the suture in one direction over a portion of the suture and barbs permitting passing of the suture in a second direction over another portion of the suture. Such an arrangement permits the passage of the suture through the tissue until the second set of barbs abut the tissue. Because the first set of barbs cannot be passed backward through the tissue and the second set of barbs cannot pass through the tissue, a firm closing stitch can be easily accomplished.
Additional methods of cutting barbs on a suture filament have been proposed (see e.g. U.S. Pat. No. 5,931,855 to Buncke).
It is seen from the foregoing that there is a need for an apparatus for cutting barbs in two directions on the exterior of sutures with a minimum of difficulty and in a precise, reliable and relatively economic fashion so as to allow for the wide spread commercialization of such sutures. Such an apparatus should also be able to vary the size of the barbs, their location and depth to allow for variation thereof and virtuality of their application. The apparatus should be able to cut a plurality of barbs positioned depending on the number of barbs needed. The configuration of the apparatus should also be variable depending upon, among other things, the type barbs being cut and the type of filament material, both of which relate to the type tissue being repaired. The apparatus should further be comprised of a series of components each of which facilitates the cutting of the barbs, these components being variable in configuration depending upon the desired features of the barbs to be cut.